In the related art, a power transmission device has been proposed which wirelessly transmits power to a power receiving device. For example, JP-A-2015-144508 discloses a wireless power transmission system which can correspond to two transmission methods and can suppress poor power transmission efficiency from the power transmission device to the power receiving device. The wireless power transmission system wirelessly transmits the power from the power transmission device to the power receiving device by using magnetic field coupling between a power transmission coil and a power receiving coil. The power transmission device has a power transmission circuit that generates an electric signal for power transmission, a first power transmission coil that corresponds to a first transmission method, a second power transmission coil that corresponds to a second transmission method, a first magnetic substance on which the first power transmission coil is placed, a second magnetic substance on which the second power transmission coil is placed, and a power supply surface on which the power receiving device is placed. A first attachment surface of the first magnetic substance and a second attachment surface of the second magnetic substance are located on a lower side of the power supply surface, and are disposed on the same plane parallel to the power supply surface. In the power transmission device, a magnetic flux generated by the first power transmission coil is concentrated inside the first magnetic substance. In this manner, the power transmission device can suppress the magnetic field coupling between the first power transmission coil and the second power transmission coil. In addition, a magnetic flux generated by the second power transmission coil is concentrated inside the second magnetic substance. In this manner, the power transmission device can suppress the magnetic field coupling between the first power transmission coil and the second power transmission coil.
Pamphlet of International Publication No. WO2011/070637 discloses a magnetic field resonance wireless power transmission system whose power transmission efficiency is improved by transmitting power using magnetic field resonance from the power transmission device to the power receiving device. A magnetic field resonance power transmission device in the magnetic field resonance wireless power transmission system includes a resonance coil, a power supply unit that supplies the power to the resonance coil so as to generate a magnetic field, a magnetic substance that changes the magnetic field generated by the resonance coil, and a position adjustment unit that adjusts a position relationship between the resonance coil and the magnetic substance. The power supply unit causes the resonance coil to generate an alternating current having a frequency the same as a transmission frequency. In a case where a measured current flowing through the resonance coil and a measured magnetic field do not reach the maximum value, the position adjustment unit adjusts a position of a magnetic field shield by rotating a position adjustment screw so that both of these reach the maximum value. Through this adjustment, a resonance frequency of the resonance coil can be adjusted to a target frequency.
JP-A-2016-005311 discloses a contactless power supply device for vehicle in which each position of a power supply coil of a housing and a power receiving coil of a portable terminal is automatically adjusted. The contactless power supply device for vehicles is installed inside a passenger compartment of a vehicle, and can support the portable terminal. The contactless power supply device for vehicles includes the housing including the power supply coil for supplying power to the portable terminal, an ECU, and a left arm and a right arm which support the portable terminal. Based on a distance between the power supply coil and the left arm and the right arm and a shape of the portable terminal detected by the ECU, the ECU detects a difference from a distance between the power receiving coil of the portable terminal and a portion of the portable terminal. The ECU controls the left arm and the right arm to move so that the difference between the distances falls within a predetermined range. Each position of the left arm and the right arm is automatically adjusted so that the power supply coil portion of the housing and a center position of the power receiving coil portion of the portable terminal are close to each other. Therefore, the contactless power supply device for vehicles can efficiently supply the power to the portable terminal, even if an occupant does not manually adjust the position.